In 1978 Daschle was elected to the United States House of Representatives, winning the race by a margin of 139 votes, following a recount, out of more than 129,000 votes cast.[13] Daschle served four terms in the House of Representatives and quickly became a part of the Democratic leadership.

Democratic losses in the November 2002 elections returned the party to the minority in the Senate in January 2003 and Daschle once more reverted to being Minority Leader.

Daschle recounted his Senate experiences from 2001 to 2003 in his first book, Like No Other Time: The 107th Congress and the Two Years That Changed America ForeverISBN 9781400049554, published in 2003.[16] With Charles Robbins, he has also written the book The U.S. Senate: Fundamentals of American Government.

In October 2001, while he was the Senate Majority Leader, Daschle's office received a letter containing anthrax, becoming a target of the 2001 anthrax attacks.[17] Many of his staffers were confirmed to have been exposed,[17] as well as several of Senator Russ Feingold's staffers and Capitol police officers.[18]

Daschle has a mixed voting record on abortion-related issues, which led the pro-choice organization NARAL to give him a 50% vote rating.[19] In 1999 and 2003, Daschle voted in favor of the ban on partial-birth abortion,[20][21] and supported legislation making it a crime to harm a fetus when someone attacks a pregnant woman.[22] (Investigators into the 2001 anthrax attacks, which included Senator Daschle's Capitol Hill office, suspect that alleged anthrax mailer Bruce Ivins may have chosen to target Daschle over his views on abortion, although Ivins's lawyer disputed this alleged motive.)[23] In 2003 Daschle's stance on abortion was reportedly criticized by Roman Catholic Bishop Robert Carlson wrote to Senator Daschle as in conflict with Roman Catholic teaching, and that he should no longer identify himself as a Catholic.[24]

In the 2004 Senate election, John Thune defeated Daschle by 4,508 votes, 50.5% to 49.4%.[25] It was the first time that a Senate party leader had lost a bid for reelection since 1952.[26] Senate majority Leader Bill Frist visited South Dakota to campaign for Thune.

Throughout the campaign, Thune, along with Frist, President George W. Bush, and Vice President Cheney, frequently accused Daschle of being the "chief obstructionist" of Bush's agenda and charged him with using filibusters to block confirmation of several of Bush's nominees. The Republican candidate also drove home his strong support for the war. In a nationally televised debate on NBC's Meet the Press, Thune accused Daschle of "emboldening the enemy" in his skepticism of the Iraq war.[27]

When the race began in early 2004, Daschle led by 7% in January and February. By May, his lead was just 2% and summer polls showed a varying number of trends: Daschle or Thune led by no more than 2%, but some polls showed a tie. Throughout September, Daschle led Thune by margins of 2-5% while during the entire month of October into the November 2 election, most polls showed that Thune and Daschle were dead even, usually tied 49-49 among likely voters. Some polls showed either Thune or Daschle leading by extremely slim margins.

Following his reelection defeat, Daschle took a position with the lobbying arm of the K Street law firm Alston & Bird. Because he was prohibited by law from lobbying for one year after leaving the Senate,[28] he instead worked as a "special policy adviser" for the firm.[29][30]

Alston & Bird's healthcare clients include CVS Caremark, the National Association for Home Care and Hospice, Abbott Laboratories, and HealthSouth.[9] The firm was paid $5.8 million between January and September 2008 to represent companies and associations before Congress and the executive branch, with 60% of that money coming from the healthcare industry.[10] Daschle was recruited by the former RepublicanSenate Majority LeaderBob Dole.[31] Daschle's salary from Alston & Bird for the year 2008 was reportedly $2 million.[32]

In late September 2005, Daschle caught the attention of the media by reactivating his political action committee, changing its name from DASHPAC to New Leadership for America PAC and procuring a speaking slot at the Iowa Democratic Party's annual Jefferson-Jackson Day dinner. He has continued to keep a relatively high profile among Democratic interest groups. These moves were interpreted by the media as an exploration of a potential 2008 Presidential candidacy. On December 2, 2006, announced he would not run for President in 2008.[34]

In addition, Senator Daschle is a Member of the Board of Trustees for the Richard C. Blum Center for Developing Economies at the University of California, Berkeley.[36] The Center is focused on finding solutions to address the crisis of extreme poverty and disease in the developing world.[37]

Tom Daschle is a Member of the Global Leadership Foundation, an organization which works to support democratic leadership, prevent and resolve conflict through mediation and promote good governance in the form of democratic institutions, open markets, human rights and the rule of law. It does so by making available, discreetly and in confidence, the experience of former leaders to today’s national leaders. It is a not-for-profit organization composed of former heads of government, senior governmental and international organization officials who work closely with Heads of Government on governance-related issues of concern to them.

In January 2005, having suggested that Obama take on some of his staffers, Daschle exited the Senate just as Obama entered.[40] These included Daschle's outgoing chief-of-staff Pete Rouse who helped to create a two-year plan in the Senate that would fast-track Obama for the presidential nomination. Daschle himself told Obama in 2006 that "windows of opportunity for running for the presidency close quickly. And that he should not assume, if he passes up this window, that there will be another."[40]

During the 2008 presidential campaign, Daschle served as a key advisor to Obama and one of the national co-chairs for Obama's campaign.[41] On June 3, 2008, Obama lost to Hillary Clinton in the Democratic primary in Daschle's home state of South Dakota, although that night Obama clinched his party's nomination anyway.

On November 19, 2008, the press reported that Daschle had accepted Obama's offer to be nominated for Health and Human Services Secretary. His selection was formally announced at a news conference with Obama on December 11, 2008.[1]

Some organizations objected to Daschle's selection, arguing that his work at Alston & Bird was tantamount to lobbying and therefore his selection violated Obama's promise to keep special interests out of the White House. According to Ellen Miller, executive director of the Sunlight Foundation, Daschle technically complies with the transition rules against lobbyists but "many power brokers never register as lobbyists, but they are every bit as powerful."[43]Stephanie Cutter, a spokeswoman for the Obama transition, responded that Daschle's work "does not represent a bar to his service in the transition" since "he was not a lobbyist, and he will recuse himself from any work that presents a conflict of interest."[43] Ron Pollack, executive director of Families USA, praised Daschle on his nomination to Secretary of Health and Human Services for his "deep commitment to securing high-quality, affordable health care for everyone in our nation."[44]

On January 30, 2009, it was reported that Daschle's friendship and business partnership with businessman Leo Hindery could cause problems for Daschle's Senate confirmation. Daschle has been a paid consultant and advisor to Hindery's InterMedia Partners since 2005, during which time he received from Hindery access to a limousine and chauffeur. Daschle reportedly did not declare this service on his annual tax forms as required by law. A spokeswoman for Daschle said that he "simply and probably naively" considered the use of the car and driver "a generous offer" from Hindery, "a longtime friend."[32][47][49][50] Daschle told the Senate Finance Committee that in June 2008—just as he was letting the press know he would like to be HHS secretary in an Obama administration[42]—that "something made him think that the car service might be taxable" and he began seeking to remedy the situation.[51]

Daschle reportedly also did not pay taxes on an additional $83,333 that he earned as a consultant to InterMedia Partners in 2007; this was discovered by Senator Daschle's accountant in December 2008.[51] According to ABC News, Daschle also took tax deductions for $14,963 in donations that he made between 2005 and 2007 to charitable organizations that did not meet the requirements for being tax deductible.[52]

The former Senator paid the three years of owed taxes and interest—an amount totaling $140,167—in January 2009,[49][50][51][53] but still reportedly owed "Medicare taxes equal to 2.9 percent" of the value of the car service he received, amounting to "thousands of dollars in additional unpaid taxes."[54]

On February 3, 2009, Daschle withdrew his nomination,[55] saying that he did not wish to be a "distraction" to the Obama agenda.[2] He was forced to withdraw because, even though he had a sufficient number of Democratic votes for nomination, he became an untenable political liability for the President.[55]

Daschle co-wrote the 2008 book Critical: What We Can Do About the Health-Care CrisisISBN 9780312383015.[56] He and his co-authors point out that "most of the world’s highest-ranking health-care systems employ some kind of 'single-payer' strategy - that is, the government, directly or through insurers, is responsible for paying doctors, hospitals, and other health-care providers." They argue that a single-payer approach is simple, equitable, provides everyone with the same benefits, and saves billions of dollars through economies of scale and simplified administration. They concede that implementing a single-payer system in the United States would be "politically problematic" even though some polls show more satisfaction with the single-payer Medicare system than private insurance.[57]

A key element of the single-payer plan that Daschle and his co-authors propose in the book is a new "Federal Health Board" that would establish the framework and fill in the details. The board would somehow be simultaneously "insulated from political pressure" and "accountable to elected officials and the American people." The board would "promote 'high-value' medical care by recommending coverage of those drugs and procedures backed by solid evidence."[58] This proposal has been criticized by conservatives and libertarians who argue that such a board will lead to rationing of health care,[59][60] and by progressives who believe the board will, as one writer put it, "get defanged by lobbyists immediately."[61]

One of Daschle's co-authors, Jeanne Lambrew, had been slated before his withdrawal to serve as his deputy in the White House Office of Health Reform.[60]